1. Field of the Invention
The present invention relates to a loop type heat pipe which can be used as a space, industrial or domestic heat transport apparatus.
2. Description of the Related Art
Among loop type heat pipes which can be used as a space, industrial or domestic heat transport apparatus, a pipe having the structure which is disclosed in, e.g., Japanese Patent Laid-Open Publication No. Hei 10-246583 has been widely used.
FIG. 6 shows the structure of a conventional loop type heat pipe. In FIG. 6, the loop type heat pipe has such a configuration that an evaporator 1 for applying heat and a condenser 20 for radiating the applied heat are connected by a vapor pipe 9 and a liquid pipe 11. A working fluid is sealed in the evaporator 1, the vapor pipe 9, the condenser 20 and the heat pipe 11. Vapor of the working fluid passes through the vapor pipe 9, and on the other hand, the liquid of the working fluid passes through the liquid pipe 11. It is to be noted that since evaporation latent heat is utilized for heat transport, a fluid having excellent vaporization properties is generally selected as the working fluid. For example, ammonia or alcohol is used as the fluid having the excellent vaporization properties.
Giving a full detail, the evaporator 1 is accommodated in an evaporator container 4. A liquid bank 6 for storing the working fluid therein is provided inside the evaporator 1, and both ends of the liquid band 6 are connected to a liquid supply pipe 17, which is connected to the liquid pipe 11 to supply a liquid 13a of the working fluid, and the vapor pipe 9, respectively. Furthermore, a second wick 7 is provided along the outer periphery of the liquid bank 6, and a first wick 2 is provided along the outer periphery of the second wick 7. The second wick 7 transports the liquid of the working fluid to the inner peripheral surface of the first wick 2 by capillary force, and the first wick 2 transports the liquid of the working fluid to the vicinity of the outer periphery of the evaporator 1 by the capillary force.
The vapor from the evaporator 1 passes through the vapor pipe 9 as indicated by an arrow 14, and the vapor 13b of the working fluid is supplied to the condenser 20, in which heat is released as indicated by arrows 21. The vapor 13b becomes the liquid 13a of the working fluid, and this liquid 13a passes to the liquid bank 6 through the liquid pipe 11 as indicated by an arrow 16.
FIG. 7 is views showing the cross section (FIG. 7(A)) vertical to the radial direction of the evaporator 1 and the cross section (FIG. 7(B)) vertical to the axial direction of the same in order to illustrate the structure of the evaporator 1 in FIG. 6 in more detail. In FIGS. 7(A) and 7(B), the first wick 2 is provided inside the evaporator container 4 forming the outline of the evaporator 1 through a plurality of projecting portions 26. Further, the second wick 7 is arranged on the inner peripheral surface of the first wick 2. A vapor flow path 25 is provided between the projecting portions 26, and the vapor 13b of the working fluid flows through the vapor flow path 25.
It is to be noted that since the first wick 2 and second wick 7 must transport the liquid 13a of the working fluid by the capillary force, a porous body having a pore diameter of approximately 0.5 to several tens of xcexcm is generally used. The pore diameter of the first wick 2 is smaller than that of the second wick 7. The first wick 2 has a function for circulating the working fluid in the loop type heat pipe by generating the high capillary force, and the second wick 7 has a function for distributing the liquid 13a of the working fluid in the circumferential direction of the first wick 2.
The second wick 7 does not, therefore, have as high a capillary force as the first wick 2 but has small flow path resistance. Thus, the second wick 7 can transport a large amount of the liquid 13a of the working fluid against the weight. A liquid bank 6 capable of storing the liquid 13a of the working fluid is provided on the inner periphery of the second wick 7, and the liquid of the working fluid is supplied from the liquid pipe 11 through the liquid supply pipe 17. Further, a vapor pipe 9 for evacuating the vapor 13b of the working fluid in the evaporator 1 is provided in the evaporator container 4.
The principle of operation of the conventional loop type heat pipe having the above structure will now be described hereinafter.
In FIG. 7, the liquid 13a of the working fluid stored in the liquid bank 6 is first transported in the circumferential direction by the capillary force of the second wick 7 as indicated by the arrow 30. Thereafter, the liquid 13a is transported in the radial direction of the first wick 2 by the capillary force of the first wick 2 which is arranged to be in contact with the second wick 7. The flow of heat to be applied at this time is indicated by an arrow. That is, when heat is applied from the outer periphery of the evaporator 1, the applied heat is conducted to the first wick 2 through the peripheral projecting portions 26 arranged between the first wick 2 and the evaporator container 4. The liquid 13a of the working fluid is evaporated to become the vapor 13b of the working fluid on the outer peripheral surface of the first wick 2 by the conducted heat. The generated vapor 13b flows in the vapor flow paths 25 along the direction indicated by an arrow 41 to enter the vapor pipe 9.
As shown in FIG. 6, the vapor 13b of the working fluid then flows into the condenser 20. However, since heat radiation is performed in the condenser 20 along the direction indicated by an arrow 21, the inside of the condenser 20 is maintained at a temperature lower than that of the vapor 13b of the working fluid. The vapor 13b of the working fluid is thus condensed and phase-changed again become the vapor 13a of the working fluid. At this time, heat radiation is carried out. Moreover, the phase-changed liquid 13a of the working fluid flows in the liquid pipe 11 as indicated by an arrow 16 and is again supplied into the liquid bank 6 through the liquid supply pipe 17.
By repeating the above-described cycle, heat can be transported from the evaporator 1 to the condenser 20.
In the above-mentioned conventional loop type heat pipe, in order to transport the liquid 13a of the working fluid to the inner peripheral surface of the first wick 2, the second wick 7 must be used. As the second wick 7, one having a pore diameter larger than that of the first wick 2 is used. Therefore, two types of wick are required, and the two-layer configuration must be employed, thereby leading to complicated manufacture.
Further, as to the liquid existing in the porous body such as a wick, the bubble nucleus which can be the nucleus of boiling generally becomes larger as the pore diameter of the porous body increases. When heated, boiling is apt to occur with a small quantity of heating. Since the second wick 7 has a large pore diameter, it has such a problem that the liquid 13a of the working fluid in the wick is readily boiled by applying heat. Therefore, when the liquid 13a of the working fluid is boiled in the second wick 7, the liquid 13a of the working fluid can not be supplied to the entire inner peripheral surface of the first wick 2 and the working fluid in the loop type heat pipe can not be thereby circulated.
In order to eliminate the above-described problems, it is an object of the present invention to provide a loop type heat pipe which can be readily manufactured without providing the double structure of the wick 2.
It is another object of the present invention to provide a loop type heat pipe by which the liquid of the working fluid is not boiled in the second wick even if a quantity of heating with respect to the evaporator is increased.
In the loop type heat pipe according to a first aspect of the present invention, grooves for transporting the liquid of the working fluid to the wick in the longitudinal direction of the wick are provided, and a liquid distribution portion for supplying the liquid is provided to the grooves. By adopting such a structure, the loop type heat pipe can be stably operated with a simple structure.
The loop type heat pipe according to a second aspect of the present invention has a liquid distribution structure for supplying the liquid to all the grooves. Adopting such a structure enables the liquid to be stably supplied to the entire inner peripheral surface of the wick without causing partial liquid distribution in the vertical direction of the evaporator.
The loop type heat pipe according to a third aspect of the present invention supplies the liquid to all the grooves by using flow paths in which the liquid flows. By adopting such a structure, the liquid can be stably supplied to the entire inner peripheral surface of the wick without causing partial liquid distribution in the vertical direction of the evaporator, and the liquid can be supplied to all the grooves with a simple structure.
The loop type heat pipe according to a fourth aspect of the present invention supplies the liquid to all the grooves by using pipes in which the liquid flows. By adopting such a structure, the liquid can be stably supplied to the entire inner peripheral surface of the wick without causing partial liquid distribution in the vertical distribution of the evaporator, and the liquid can be reliably supplied to all the grooves.
The loop type heat pipe according to a fifth aspect of the present invention has a liquid distribution structure for supplying the liquid to part of the grooves. Adopting such a structure enables the liquid to be efficiently supplied to the inner periphery of the wick.
The loop type heat pipe according to a sixth aspect of the present invention has a flow path in which the fluid can flow and supplies the liquid to part of the grooves by using this flow path. When such a structure is employed, the liquid can be supplied to an arbitrary groove by the simple structure.
The loop type heat pipe according to a seventh aspect of the present invention uses a pipe in which the liquid flows to supply the liquid to part of the grooves. Adopting such a structure enables the liquid to be reliably supplied to an arbitrary groove.